A Genetic Study of Plant Height in Phaseolus Vulgaris. 47 
would be strikingly different in the two plants. And, if a number 
of such cases occurred, the coefficient of variation in mean length 
of the first five internodes might be very high, even tho the ulti- 
mate heights of the several plants were almost the same and the 
mean length of the first 15 internodes showed little variation. 
That just such differences in the initiation of growth-rate acceler- 
ation did occur in the July bean is shown by the measurements of 
the first six internodes of two plants of the same family (3,434) 
that ultimately reached approximately the same heights. The 
individual internode lengths in millimeters were: 
The total lengths of the first five internodes were 298 mm. and 
215 mm. and the mean lengths, therefore, 59.6 mm. and 43.0 mm., 
respectively. The total lengths of the first 15 internodes of these 
same two plants were 1,579 mm. and 1,619 mm. and the corres- 
ponding mean internode lengths, therefore, 105 mm. and 108 mm., 
respectively. In short, July bean plants may exhibir great dif- 
ferences in mean length of the first five internodes and almost no 
difference in mean length of the first 15 internodes. 
In this connection the relative variation in length of particular 
internodes is worth noting. The coefficients of variation for each 
of the first five and for the tenth internodes of July (83 plants) 
and Snowflake (78 plants) are given below: 
July shows considerably more variation than Snowflake in the 
third, fourth, and fifth internodes, somewhat less in the tenth 
internode, only slightly more in the second internode, and no 
appreciable difference in the first internode. While the coefficient 
of variation for mean length of the first five internodes of July 
was 32.67 ±2.64 per cent and that of Snowflake 15.81 ±1.01 per 
cent (Table 4), or a difference of 16.86 ±2.83, these constants 
for the first 15 internodes (Table 5) were for July 26.11 ±1.52 
per cent and for Snowflake 27.68 ±1.86 per cent, an insignificant 
difference of 1.57 ±2.40. As will be shown later, when the first 
15 internodes instead of only the first five are considered, segre- 
gation of internode length factors in Fa is more plainly indicated. 
Internode No 
First plant ... 
Second plant . . 
1 2 3 4 5 6 
22 16 38 96 126 220 
20 17 39 54 85 176 
First internode . . 
Second internode 
Third internode . . 
Fourth internode 
Fifth internode . . 
Tenth internode . 
July Snowflake Difference 
17.08±0.95 16.77±0.90 0.31±1.31 
24.36^1.17 20.76^1.35 3.60±1.79 
35.40±1.33 23.48±2.07 11.92±2.46 
47.16±1.78 30.29±2.97 16.87±3.46 
45.25±1.35 23.74±2.81 21.51±3.12 
28.29^2.24 35.55±1.61 -7.26±2.76 
